There are some very simple porous elements on the market that consist of a cylindrical rod made mainly of rolled paper impregnated with volatile substances. An example of these types of products is described in document WO2006/02395.
These very simple products are designed to be disposed on a support or hanged and to release the volatile substances under static conditions.
The use of these types of rolled and impregnated paper elements for evaporating volatile substances has various drawbacks.
On the one hand, the manner in which this paper is rolled makes the level of compaction higher in the centre than along the perimeter, reducing the capacity of the core to act as a receptacle for volatile substances.
On the other hand, its surface cannot be altered mechanically to increase the evaporation surface, since a cut in the external paper layer would cause the entire wrapping to break.
There is also the alternative of using wooden rods, but this type of material generally either has high porosity to contain volatile substances, but are mechanically weak or have a high level of density when they have poor absorption capacity but good mechanical resistance.